First, I would confirm the error, and what it was about. If the balance due was too low, I would determine if we can live with, or eat, the shortfall. If the balance was too high, I would de3termine what caused the error, prepare a new invoice immediately, then call the client.

Once I speak to the client, and explain that there was an error, I would likely ask that that invoice be destroyed. A new invoice is on its way, immediately if needed, in mail if client understands the issue and agrees that errors happen.

The error made will dictate the response. If a math error in goods sold, that's easily explained. If for professional services, perhaps for hours charged or services rendered, an explanation must be delivered to the client if they have received the erroneous invoice. An explanation of what to expect should be delivered during the phone call.

Once the issue has been discussed, and resolution arrived at, prompt delivery of the revised invoice is appropriate. Follow up after a few days, by the same person who called to clarify the invoice, is a good idea to insure the client understands the correction and agrees with it.

small errors that we could live with can be accepted to promote goodwill. A bill that should be $6,300 but is issued by $6,000 might be small enough to pass on. The amount of additional income might not be worth alienating a client.